The effects of dietary lipids on dendritic cells in perinodal adipose tissue during chronic mild inflammation

The effects of dietary lipids on the abundance of dendritic cells in adipose tissue in anatomically defined relationships to chronically inflamed lymph nodes were investigated in mature male rats fed plain chow or chow plus 20% sunflower-seed or fish oil. The popliteal lymph nodes were stimulated by local subcutaneous injection of 20 jig lipopolysaccharide to both hindlegs three times/week for 2 weeks. The masses of the major adipose depots and the numbers of dendritic cells emerging from perinodal adipose tissue and samples 5 and 10mm from the popliteal lymph nodes were measured, and those from omental and mesenteric adipose tissue around and remote from lymphoid tissue, and mesenteric and popliteal lymph nodes. Dendritic cells were most numerous in the perinodal adipose tissue, with the corresponding 'remote' samples containing 25-50% fewer such cells under all conditions studied. Dietary sunflower-seed oil increased the numbers of dendritic cells by about 17% in all adipose samples and fish oil reduced the numbers in perinodal tissue by about 5%. The fish-oil diet diminished responses of the intra-abdominal adipose depots to local stimulation of the popliteal node. Correlations in dendritic cell numbers were stronger between perinodal samples from different depots than between remote and perinodal samples from the same depot and; after the sunflower-seed-oil diet compared with fish oil. These data show that dietary lipids modulate the number of dendritic cells in lymphoid tissue-containing adipose depots and support the hypothesis that perinodal adipose tissue interacts locally with lymphoid cells.